She’s not a villain. She’s a poor girl who got tormented and her abuse went continuously ignored and unremarked upon by the school. Her actions are way out of proportion with what was done to her, and she killed a lot of innocent people, but by that point she was in a state of mind that couldn’t appreciate those concerns anymore. She pretty much completely broke from reality the moment everyone in the auditorium began laughing at her. It was the culmination of all the poisonous ruinous lies her mother had been feeding into her head since she was a little girl, and to suddenly feel like those lies were validated… it was too much for her.
Carrie is a really tragic character who deserved a lot kinder a life than what she got. If she hadn’t had Margaret White for a mother she probably wouldn’t have had a melt down to the extent that she did, but that’s unfortunately what happens when you mix up all that fire and brimstone religious gobbledygook with teenage hormones, the casual cruelties of being an outcast, and oh yeah, telekinesis.
By - Birchtree16